Patients prone to irregular heart rhythms sometimes have miniature heart devices, such as defibrillators and cardioverters, implanted in their bodies. These devices detect onset of abnormal heart rhythms and apply corrective electrical therapy to the heart. The defibrillator or cardioverter includes a set of electrical leads, which extend from a device housing into the heart. Within the device housing are a battery for supplying power, circuitry for detecting abnormal heart rhythms, and a capacitor for delivering bursts of electric current through the leads to the heart. Since defibrillators and cardioverters are typically implanted in the left region of the chest or in the abdomen, a smaller size device, which is still capable of delivering the required level of electrical energy, is desirable.
The basic components that make up a battery are an anode, a cathode, a separator between the anode and the cathode, electrolyte, and packaging hardware such as the case. Batteries can be of a wound, jellyroll, style of design that may be cylindrical or flattened cylindrical in shape. Some designs fold the battery components on top of one another.
The anodes and cathodes of the battery are opposed to each other throughout the battery. This continuous opposition requirement creates packaging inefficiencies, such as wasted volume at bend lines or, in the wound configuration, the mandrel volume itself. Moreover, these folded or wound design approaches are limited to simple cross-sectional areas due to the manufacturing constraints of producing such a battery cell. It is desirable to improve the packaging efficiency of the battery particularly for medical implantable devices, since this will provide a smaller battery. Also, consistency from one battery to the next is a desirable feature for implantable medical devices. A heightened consistency allows the battery's life-cycle to be predictable and allows the battery to be replaced at an opportune time without emergency.